Nonclogging centrifugal pump



Jan. 26, 1965 L. H. SENCE NONCLOGGING CENTRIFUGAL. PUMP 2 Sheets-Sheet 1Filed April 15, 1963 1965 H. SENCE 3,167,021

NONCLOGGING CENTRIFUGAL PUMP United States Patent 3,167,021 NONCLOGGINGCENTRIFUGAL PUMP Leonard H. Sauce, Milford, Ohio, assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis. Filed Apr. 15, 1263,Ser. No. 273,164 2 Ciaims. ((11. 103-4103) This invention relatesgenerally to centrifugal pumps. More specifically this invention relatesto nonclogging, solids handling centrifugal pumps.

There has long been a problem in the hydraulic industry in connectionwith pumping solid material or fibrous material. These materials tend toclog the impeller of a centrifugal pump. However, there is a trendtoward pumping more and larger solid material suspended in liquids. OneWay of solving this problem is to take a conventional centrifugal pumpimpeller and position it in a recessed area alongside a swirl or pumpingchamber. The impeller is spaced from the opposing wall of the pumpoasing a distance equal to the diameter of the inlet of the pump so thatany material entering the pumping chamber can be pumped outward throughthe discharge without engaging the impeller vanes. Although pumps ofthis type have been successful to a certain degree, they can onlydevelop a very limited head and their efficiency is extremely low. As aresult, such a pump is used only where it is absolutely necessary topump solids of such a size that they frequently clog the impeller of aconventional centrifugal pump.

Applicant overcomes the problemsmentioned above by providing a uniqueimpeller which permits the use of the vanes in the pumping chamber andis still capable of pumping any solid which enters the inlet of thepump. The impeller vanes are formed so that they are very narrow nearthe center of the impeller and gradually widened to a distancesubstantially equal to the distance across the impeller chamber near theperiphery of the impeller. The vanes are arranged so that when theimpeller is in the pumping chamber with the edges of the vanes almosttouching the opposing wall surface, the vanes combine with the backplateof the impeller and the casing to define a passageway extending from theeye of the impeller to its periphery which has a minimum size equal to asphere of the same diameter as the inlet of the pump. Such a pump whichis fully described in applicants copending US. patent application SerialNo. 243,112, now Patent No. 3,130,679, is nonclogging in that there is acontinuous path through the pumping chamber which is the equivalent sizeof a sphere equal to the diameter of the inlet.

Experience in operating the above described pump has shown that aninteresting and unusual phenomenon occurs when the impeller is movedaway from the opposing wall surface of the impeller chamber. The head,rather than dropping sharply as expected on the basis of experience withconventional centrifugal pumps, remains substantially the same until theimpeller is withdrawn completely out of the impeller chamber.Furthermore, the pumps efiiciency remains high during the same period.These unusual and highly desirable results are due at least in part tothe unique formation of the impeller blades which actually exert a forceon the swirling Water in the impeller chamber as the water is forcedradially out of the chamber. In comparable prior art, solids handlingpumps such as shown in US. Patents 2,958,293, R. F. Pray, Ir., and2,635,548, C. H. Brawley, a swirl of liquid is formed in the pumpingchamber by the blades positioned just outside of the pumping chamber andthe swirling liquid imparts the force on the incoming liquid and solidsbeing pumped. Hence, there is a significant loss of both efilciency andhead. On the other hand, in the pump of this invention, substantiallyall the liquid being pumped enters the eye of the impeller and is thrownradially outward. As the liquid flows radially outward, it also flowsaway from the backplate or shroud of the impeller. However, in this areathe vanes also extend further away from the shroud and hence stillengage the water being pumped and continue to exert a direct force onit. It is believed that this type of action which occurs even when theimpeller is retracted almost entirely out of the impeller chamberaccounts for the unusually high efl'iciencies and head of this pump inall positions of the impeller. A pump with a retractable impeller isespecially useful in pumping long stringy material which tends to ballup or get stuck between the impeller vanes and the pump casing.

Therefore, it is the object of this invention to provide a new andimproved centrifugal pump.

Another object of this invention is to provide a nonclogging solidshandling pump with improved head and efliciency.

Another object of this invention is to provide a new and improvednonclogging solids handling pump having an impeller that is movableaxially within the pumping chamber.

Other objects and advantages will be apparent from the followingdescription when read in connection with the accompanying drawings inwhich:

FIG. 1 is a cross sectional view of a centrifugal pump embodying theimpeller of this invention;

FIG. 2 is an end view of the impeller of this invention taken along thelines lIII of FIG. 1;

FIG. 3 is a graph comparing the capacity, head and efficiency of a pumpof this invention run at 1150 r.p.m. with the impeller in a fullyretracted, 50 percent retracted and a nonretracted position; and

FIG. 4 is a graph plotting the percent head and efficiency againstpercent opening of the impeller with the pump capacity held constant.

The pump assembly 9 illustrated in FIG. 1 comprises generally a pumpcasing 10 having an inlet 11 and a discharge 12. The casing 10 definesan impeller or pumping chamber 13 in which an impeller 14 of thisinvention is normally positioned. The chamber 13 has a peripheral volute15 to gather the discharge from the impeller and direct it into thedischarge nozzle or opening 12.

The impeller 14 is connected to a shaft 17 which extends rearwardly fromthe pump casing 11) to a source of power. The shaft 17 is surrounded bya conventional shaft sleeve 16 and a suitable seal illustrated as astufling box 18 having the usual packing 19 and a gland 20. The shaft 17is also surrounded by a bearing and bearing cartridge 23 which is inturn mounted in a bearing bracket 24. The bearing bracket is in turnconnected to the pump casing 10 and a base member 25.

The pump 9 is also equipped with a rear cover plate 28 which in thisparticular embodiment surrounds the stufiing box 18 and is positioned ina cylindrical neck portion 30 of the pump casing 10 a distance equal tothe width of the impeller so that the impeller can be with drawnentirely out of the chamber 13 into the neck portion 30.

The impeller has a rear shroud 29 having a hub portion 39 with an axialbore 40 formed therein. The bore 40 is threaded for connection to theend of the shaft 17. As shown in FIG. 2, vanes 35 are arcuately spacedaround the shroud 29 and extend from near the hub 39 to the periphery.The thickness 42 of the vanes as shown in FIG. 2 is substantially thesame throughout their length although it could be varied if desired.However, the

width 43 of the vanes 35 shown in FIG. .1 varies from a very narrowwidth near the hub 39 of the impeller to a maximum width near theperiphery of the impeller at which point the width of the vanes issubstantially equal to the width of the impeller chamber 13.

The vanes 35 are so formed that when the impeller 14 is in thenonretracted position with the edges of the vanes almost touching theopposing wall 36 of the impeller chamber 13, the vanes, the shroud plate29 and the wall 36 combine to define a plurality of fluid impellingpassages 45 that extend from the inlet end of the pump to the discharge.The minimum size of these passageways 45 with the impeller in thenonretracted position is equivalent to a sphere of the same diameter asthe inlet 11 of the pump. Hence, any solid material entering the inletof the pump can pass through one of these passages through the impellerchamber into the discharge regardless of the position of the impeller.The minimum size of these passages is made possible by forming theleading edge 46 of the vanes so that it curves away from the wall 36 ofthe impeller chamber 13 near the hub of the impeller where the arcuatespace between adjacent vanes is very small. In this area the distancebetween the edge 46 of the vane and the wall 36 of the casing is substantially equal to the diameter of the inlet.

As the vane extends radially outward, the edge 46 of the vane curvestoward the opposing wall surface 36 of the impeller chamber. In areasradially outward from the hub, the sphere can move between adjacentvanes 35 and a portion of the sphere extends inwardly from the edge ofthe vanes toward the shroud plate 2 of the impeller. In this position itdoes not require as much space between the edge 46 of the impeller vaneand the casing wall 36 to pass a sphere the size of the inlet. For thisreason the edge of the vane. can extend closer to the opposing wallsurface as the vane extends radially outward. The curve on the edge ofthe vanes continues until a point is reached where the distance betweenadjacent vanes is equal to the diameter of the inlet or the diameter ofthe theoretical sphere which is to be passed through the pump. At thispoint, depth of the blades or vanes 35 is substantially equal to thewidth of the chamber 13.

In some applications, the material being pumped consists of long stringymaterial such as rags and intestines of animals. Such material tends towind itself around the impeller vanes and wedge into narrow spacesbetween the vanes and the opposing wall surfaces. This problem can beovercome by moving the impeller away from the opposing wall surface 36 asufiicient distance to prevent any clogging between the impeller and thecasing wall.

In the pump of this invention, means are provided for moving the shaft17 and the impeller 14 axially relative to the pump casing to vary thedistance between the opposing wall surface 36 and the leading edge 46 ofthe impeller vanes. Any suitable means may be provided for moving theimpeller relative to the wall but as specifically shown in FIG. 1, thebearing cartridge 23 is slidably mounted in the bearing bracket 24, andan adjusting mec, anism 49 is provided for moving the cartridgerelative. to the bracket and locking it in place. The adjustingmechanism 49 has a flange th with a bore 51 formed therein attached toand extending outwardly from the bearing cartridge 23. The flange 50 andbore 51 are aligned with a suitable flange 52 and threaded bore 53 onthe bearing bracket 24-. A suitable bolt 54 extends through the bore 51in flange 5i) and threadedly engages the bore 53 in flange 52 for movingthe bearing cartridge relative to the bearing bracket. A nut 55threadedly engages the bolt 54 and is forced into abutting relation withthe flange 50 to lock the adjusting mechanism 49 and hence the bearingcartridge in position.

With this adjusting mechanism 49, the impeller can be anywhere between afully closed position shown in solid lines in FIG. 1 and the retractedposition shown in the dot-dash lines in FIG. 1 and identified as 14'. Anintermediate position with the impeller approximately half way betweenthe retracted and nonretracted positions is also shown in dot-dash linesin FIG. 1 and is identified The results of the recent tests of the pumpof this invention run at 1150 rpm. are summarized in the curve of FIG.3. The three head capacity lines are labeled Non-Retracted, 50%Retracted and Retracted, respectively, to indicate the position of theimpeller relative to the wall 36 and correspond to the impellerpositions in FIG. 1. In the nonretracted position, the impeller isadjacent the side wall, in the retracted position the impeller iswithdrawn into the neck portion 38, and in the 50 percent retractedposition the impeller is positioned midway in the impeller chamber 13.The pump efficiency is shown in the form of constant efficiency lines A,B and C superimposed on the three head capacity lines. This shows thatthere is an eificiency loss from nonretracted to 100 percent retractedof about seven points. In percentage loss in eiiiciency, this is abouttwelve points.

The moderate loss in head as shown by the curves shown in F G. 3 is adistinct advantage, since the system head against which a pump of thistype is normally working will be fairly constant. Assuming for instancethe system head to be represented by line DE at 55 feet, then the pumpcould operate at points F, G or H, and still overcome the system head.Thus, various retracted positions might be taken'by the impeller up tofully retracted with the pumping head being maintained high enough toovercome the static head of the system, although at reduced capacity(g.p.m.). In a conventional open impeller pump designed to operate withthe impeller vanes fitted closely to the casing front cover, a similarretraction would reduce the head values by almost fifty percent, so thatthe pump in many applications would be unable to overcome the systemhead. In a nonclogging pump, it is a distinct advantage to be able toretract the'impeller when desired and still maintain the total developedhead near full value.

In the graph shown in FIG. 4, the characteristics of the pump of thisinvention are plotted in a slightly different manner. This curve showsthat with constant capacity, the pump efficiency measured from point ofmaximum elficiency and developed head drop off only slightly as thepercent of opening or retraction increases from 0 percent to 100percent. strate two of the principal advantages of the present nonclogpump, namely, that of holding the developed head values to keep theliquid flowing against the system head and also the economy of powerconsumption represented by the efliciency line.

Below the curves of this pump is another curve showing thecharacteristics for another open impeller adjustable pump made byAllis-Chalmers. The characteristics of this pump are similar to those ofother open impeller adjustable pumps presently on the market. In thispump, which we have identified as pump X, as the percent openingincreases froni zero value the, head loss is very marked. For example,at 10 percent opening the head loss is 25 percent. Hence, theretractability of the impeller in this pump is a highly criticaladjustment especially if the pump is part of a system pumping against afixed system head. A very slight retraction of the impeller in such apump may interrupt the continuity of flow unless other remedies aretaken, such as speeding up the pump or reducing the system head.

In operation, as the impeller 14 begins to rotate, liquid with solidsentrained therein are drawn in through the inlet 11. This liquid is thenacted upon by the impeller and thrown radially outward. Any solids inthe liquid move through the impelling passages 45 defined between thevanes 35, the internal wall surface 36 of the impeller chamber and therear shroud 29. In this way, any solid which can enter the inlet of thepump can be impelled through the impeller into the discharge withoutclogging the pump.

If it is desired to change the position of the impeller 14 in thechamber 13, the nut 55 is loosened and the bolt Si? is rotated in theproper direction to vary the relative These substantially fiat curvesdemonpositions of the bearing cartridge and the pump casing. Forexample, to move the impeller away from the wall 36, the bolt 50 isrotated in a counterclockwise direction and the nut 55 is tightenedagainst flange 50 to move the cartridge, shaft and impeller away fromthe wall 36 until the nut engages flange 50 to lock the adjustingmechanism and the cartridge, shaft and impeller in place. To move theimpeller closer to the wall 36, the nut is loosened and the bolt 54 isrotated in a clockwise direction to move the flange 50, cartridge 23,shaft 17 and impeller 14 toward the wall 36 When the desired position isachieved, the nut 55 is again tightened against the flange 50 to lockthe part in place.

Although but one embodiment of this invention has been illustrated anddescribed, it will be apparent to those skilled in the art that variousmodifications and changes can be made therein Without departing from thespirit of the invention or the scope of the appended claims.

Having now particularly described and ascertained the nature of my saidinvention and the manner in which it is to be performed, I declare thatwhat I claim is:

1. A centrifugal pump comprising: a casing having walls defining animpeller chamber and a cylindrical neck portion extending therefrom,said chamber having an axial inlet and a radially spaced dischargeopening, an impeller mounted for rotation in said chamber, said impellerhaving a rear shroud plate and a plurality of arcuately spaced vanesmounted thereon, said vanes extending from the periphery of said plateradially inward to near the center of said impeller, the depth of saidvanes being smaller near the center of said impeller than near its outerperiphery, the depth of the radially outer portion of said vanes beingsubstantially equal to the width of said chamber, said vanes beingarranged on said impeller so as to define with said shroud plate and theopposing wall of said impeller chamber a plurality of passagescontinuous from the inlet of said chamber to said outlet, adjustingmeans for moving said impeller axially be tween a position adjacent saidoposing wall and a position substantially within said neck portion andoutside of said chamber, the minimum size of said passages for anyposition of said impeller being at least equal to a sphere of the samediameter as the width of said inlet, whereby any solid body enteringsaid chamber through said inlet can be passed through said impeller tosaid discharge for any position of said impeller.

2. A centrifugal pump comprising: a casing having walls defining animpeller chamber and a cylindrical neck portion extending therefrom,said chamber having an axial inlet and a radially spaced dischargeopening, an impeller mounted for rotation in said chamber, a shaftconnected to said impeller and extending through said neck portion andout of said casing, said impeller having a rear shroud plate and aplurality of arcuately spaced substantially radially extending vanesmounted thereon, said vanes extending inward to near the center of saidimpeller, the depth of said vanes being smaller near the center of saidimpeller than near its outer periphery, the depth of the radially outerportion of said vanes being substantially equal to the Width of saidchamber, said vanes being arranged on said impeller so as to define withsaid shroud plate and the opposing Wall of said impeller chamber aplurality of passages continuous from the inlet of said chamber to saidoutlet, a bearing bracket connected to said pump casing, a bearingcartridge slidably mounted in said bracket and surrounding said shaft,means to prevent axial movement of said shaft relative to saidcartridge, means adjustably engaging said cartridge and said bracket tovary the position of said cartridge relative to said bracket and therebymove said impeller axially between a position adjacent said oposing walland a position substantially within said neck portion and outside saidchamber, the minimum size of said passages for any position of saidimpeller being at least equal to a sphere of the same diameter as theWidth of said inlet, whereby any solid particle entering said chambercan be passed through said impeller to said discharge for any positionof said impeller.

References Cited in the file of this patent UNITED STATES PATENTS952,993 Mathis Mar. 22, 1910 2,693,312 Lanter Nov. 2, 1954 2,874,642Forrest Feb. 24, 1959 3,010,402 King Nov. 28, 1961 FOREIGN PATENTS1,055,511 France Oct. 19, 1953 808,796 Germany July 19, 1951 413,573Great Britain July 19, 1934 441,385 Great Britain Jan. 20, 1936 574,079Great Britain Dec. 19, 1945 82,497 Switzerland Oct. 1, 1919

1. A CENTRIFUGAL PUMP COMPRISING: A CASING HAVING WALLS DEFINING ANIMPELLER CHAMBER AND A CYLINDRICAL NECK PORTION EXTENDING THEREFROM,SAID CHAMBER HAVING AN AXIAL INLET AND A RADIALLY SPACED DISCHARGEOPENING, AN IMPELLER MOUNTED FOR ROTATION IN SAID CHAMBER, SAID IMPELLERHAVING A REAR SHROUD PLATE AND A PLURALITY OF ARCUATELY SPACED VANESMOUNTED THEREON, SAID VANES EXTENDING FROM THE PERIPHERY OF SAID PLATERADIALLY INWARD TO NEAR THE CENTER OF SAID IMPELLER, THE DEPTH OF SAIDVANES BEING SMALLER NEAR THE CENTER OF SAID IMPELLER THAN NEAR ITS OUTERPERIPHERY, THE DEPTH OF THE RADIALLY OUTER PORTION OF SAID VANES BEINGSUBSTANTIALLY EQUAL TO THE WIDTH OF SAID CHAMBER, SAID VANES BEINGARRANGED ON SAID IMPELLER SO AS TO DEFINE WITH SAID SHROUD PLATE AND THEOPPOSING WALL OF SAID IMPELLER CHAMBER A PLURALITY OF PASSAGESCONTINUOUS FROM THE INLET OF SAID CHAMBER TO SAID OUTLET, ADJUSTINGMEANS FOR MOVING SAID IMPELLER AXIALLY BETWEEN A POSITION ADJACENT SAIDOPPOSING WALL AND A POSITION SUBSTANTIALLY WITHIN SAID NECK PORTION ANDOUTSIDE OF SAID CHAMBER, THE MINIMUM SIZE OF SAID PASSAGES FOR ANYPOSITION OF SAID IMPELLER BEING AT LEAST EQUAL TO A SPHERE OF THE SAMEDIAMETER ASD THE WIDTH OF SAID INLET, WHEREBY ANY SOLID BODY ENTERINGSAID CHAMBER THROUGH SAID INLET CAN BE PASSED THROUGH SAID IMPELLER TOSAID DISCHARGE FOR ANY POSITION OF SAID IMPELLER.